New insight into strong correlated states realised in a ferroelectric and paraelectric chalcogenide Sn2P2S6 crystal

Abstract

In the present study, the electronic properties of both ferroelectric and paraelectric phases of the Sn₂P₂S₆ (SPS) chalcogenide crystal were investigated using first principles methods. Via applying the density functional theory methodology (DFT) with different functionals, their energy band structures were calculated and discussed. It was confirmed that the pure DFT methodology as well as that extended by the hybrid functionals did not provide a satisfactory result in the prediction of the electronic parameters of the SPS crystals. To improve the theoretical modelling of the abovementioned materials, the Hubbard correction was proposed in this study, and as a consequence, the appropriate electronic parameters were obtained. The correct values of the band gap for the para- and ferroelectric phases of the SPS were obtained by applying the Hubbard parameters for the p orbitals of the S and P atoms. Moreover, the influence of the Hubbard parameters on the charge transfer between atoms was shown and analyzed. In this case, the electronic character of the (SP₃) subsystem was explained and the role of the Sn atoms in the investigated chalcogenide systems was described.